THE GRASSHOPPER 23 



The Thorax. — (i) Remove the wings, that the thorax 

 may be more plainly seen. 



Back of the head is the prothorax, or collar. Notice 

 its shape on the dorsal and lateral sides. The dorsal side is 

 called pronotum. Does it extend around the body? What 

 is the shape of the ventral side? What causes that peculiar 

 structure ? It is called pr asternal spine. Does the prothorax 

 on the dorsal side seem to be divided into segments? How 

 many? 



(2) Look carefully at the remainder of the thorax. Is it 

 divided into segments? What indicates the segments? Do 

 they extend all around the body? The segment next the 

 prothorax is the mesothorax, and the last one, the meta- 

 thorax. What peculiarity do you notice on the ventral side 

 of the thorax ? 



(3) The ventral side of the entire animal is called the 

 sternum, the lateral side the pleurum, and the dorsal side the 

 tergum. Note the differences in color and hardness of these 

 parts. 



How many legs on the ventral side? Observe the place 

 and mode of attachment to the body. The sockets for at- 

 tachment are called coxal cavities. How many divisions in 

 each leg? In the front pair of legs find the following parts, 

 beginning with the body : coxa, trochanter, femur, tibia and 

 tarsus, or foot. The tarsus is subdivided into segments. 

 How many do you find ? Notice the relative size, shape, and 

 markings of each segment. 



Does each pair of legs have the same divisions with the 

 same relative sizes? 



When a part of an animal is unusualy large or has a 

 peculiar shape for the performance of a special work it is 



